When does the Catchdog let go?

I've always used a breakstick.....but hunted with a few that used the same pull up on the collar method as Mike said and that seemed to work great as well. Could never understand why some would smack their dog with a flashlight or fist to break them off.........They teach their dog to catch and then in a split second punish it for doing what it was taught.....I dont believe any good catch dog should have the "lightswitch" speed to turn on and off with a verbal command......and at the same time shouldn't be struck to let go of what he is suppose to be caught on......
just my 2 cents.....